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Topics Included:
• Physical Quantities
• Traditional Units of Measurement
• Standard Units of Measurement
• Other SI systems
• Measuring Length
→ Ruler
→ Meter Rod
• Measuring Length of a Curved Line
→ The thread method
→ The divider method
• Measurements in daily life
• Estimation and its Importance in real life
• Motion
• Rest and Motion
• Types of Motion
2. Physical Quantities
• The quantities that can be measured
are called physical quantities. For
measuring the physical quantities, we
require magnitude and a fixed unit. For
example, If the distance from London to
Reading is 275 km, so the magnitude is
275 and its unit is km here.
• The specific physical quantities that
cannot be expressed in any other
quantity are called fundamental
physical quantities. Some fundamental
physical quantities are mass, length,
time and temperature.
3. Traditional Units
of Measurement
In ancient times, people use their hands, arms and feet to
measure the quantities. These methods still use in the present
time. The units that we measure through these methods are
yards, cubit and handspan.
Units Description
Yard The distance between the endpoint of an outstretched arm to the
tip of the nose.
Cubit The distance between the elbow to the tip of the middle finger.
Foot Measurement of the quantity by a barefoot of an adult person.
Handspan The measurement of a quantity by the tip of the thumb to the tip
of the little finger when the palm is outstretched.
4. Standard Units of Measurement
Quantities SI units Symbol
Length metre m
Mass kilogram kg
Time second s
The standard units of measurement
introduced to measure accurate quantity of
any object.
In 1960, the General Council of Weights and
Measures organized where all the scientists
gathered to decide the uniform system of
units acceptable all over the world.
5. Other SI systems
• The measurement of smaller quantities is
called submultiples of units. They represent
with the factor of 1/10, 1/100 and 1/1000, etc.
• The measurement of larger quantities is called
multiples of units. They represent with the
factor 10, 100 and 1000, etc.
• Both multiples and submultiples have prefixes
and symbol.
Prefixes Symbol Submultiples/Multiples
deci d Submultiple: 1/10
centi c Submultiple: 1/100
milli m Submultiple: 1/1000
Kilo k Multiple: 1000
Hecto h Multiple: 100
Mega M Multiple: 10000
Terms Description
CGS Centimetre for length, Gram for mass and Second for time
MKS Metre for length, Kilogram for mass and Second for time
FPS Foot for length, Pound for mass and Second for time
6. Measuring Length
The measurement of length concerns the length, width, thickness, height and distance
of any object.
There are several instruments used to measure the length. For example, a ruler, metre
rod and a measuring tape, etc.
• A ruler has units of centimeter and millimeter.
It is used to measure smaller quantities
• A meter rod is used by tailors to measure the
length of the cloth. The unit of meter rod is
fixed to one meter.
7. Measuring Length of a Curved Line
The divider method
1
i. Take a pair
of dividers
and separate
them with
the help of a
scale.
2
ii. Put the
one tip of the
divider at the
one end of
the curved
line and
another tip
of divider at
the curved
line by taking
markings.
3
iii. Repeat
this process
until the
whole line is
divided into
segments.
4
iv. If any
segment is
left over
then
measure the
length by a
formula
shown
below.
The thread method
1
i. Take a long
thread and
mark one of
its ends.
2
ii. Put the
marked end
of the thread
at the
starting of
the curved
line by using
your thumb.
3
iii. Put the
other end of
the thread to
the other
side of the
curved line
by another
thumb of
your other
hand.
4
iv. Lastly,
stretch the
thread to
measure the
length.
The length of a curved line :
(Number of segments of equal lengths x distance between the tips of the divider) + length of the left-over part
9. Estimation
The ability of guessing the value of anything without calculating the
accurate value of the object is called the estimation.
Eg: by planning a trip, we assume the approximate cost and time.
Estimation helps in daily tasks when we
must estimate time, money or any
other quantity.
When you're shopping in the grocery
store and trying to stay within a
budget, for example, you estimate the
cost of the items you put in your cart to
keep a running total in your head.
Importance of
Estimation in Real Life
11. Motion
The changing in the position of any object concerning
time regarding the effects of its surroundings is called a
motion. For example, driving a car.
If an object is fixed at a particular position, then there is
no changing of the position called stationary or at the
rest. For example, trees are fixed at a particular place.
Living things move on their own, but non-living things
do not move on their own. For example, a car needs a
driver and fuel to move.
12. Rest and Motion are Relative.
The state of being at rest or in motion is always relative to a certain object.
For example: Suppose you and your father sitting in a car and your mother is standing
in the street. When the car moves, your father is at rest to you but not to your mother.